Night vision goggles and similar optics systems have been widely used by military personnel and civilians to enhance viewing during nocturnal activities and in other low illumination conditions. Many night vision devices operate at low light levels by amplifying a received light pattern. As used herein, the term light is broadly defined and includes, but is not limited to, electromagnetic radiation in the visual spectrum, the infrared range and the ultraviolet range. The received light is light that has been reflected off of objects and/or emitted by objects to form an image. After passing though a lens assembly to focus the received light, a photomultiplier tube amplifies the light and a corresponding image is presented to the user with a phosphor screen. In this arrangement, the user's vision is through the night vision device and the user has no direct image of the environment before him or her.
In most situations, and especially in military applications, the user needs to be able to view things at a distance (e.g., enemy combatants, a roadway, etc.) as well as things closely located to the user (e.g., the terrain around the user's feet, hand operated equipment and so forth). Conventional night vision equipment includes a manually operated focus device to adjust the focal point of the focusing optics and/or a mechanism to switch between a near field viewing mode and a far field viewing mode. Using these devices can be tedious and time consuming. Changing the focus can also distract the user's attention away from more pressing matters, such as operating a vehicle or engaging enemy combatants.
When the night vision equipment is focused for far field objects, soldiers have complained that they cannot clearly see obstacles near their feet or equipment that they need to operate. Accordingly, the soldier's mobility is adversely affected by the focus settings of the night vision equipment. Similarly, when the equipment is focused for near field objects, the soldiers cannot clearly see objects at any appreciable range, which also compromises the soldier's ability to carry out an objective.
Attempts have been made to automatically adjust the focus of the night vision equipment, but these systems have used motorized assemblies that add a significant amount of weight to the equipment. The added weight can be burdensome to users of a head mounted night vision system. These systems also include complex electronics to track the user's eye movements and may not be able to refocus the focusing optics fast enough to adequately perform in stressing situations.
Accordingly, there is a need in the art for an improved night vision assembly that allows a user to clearly view near field and far field objects.